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See also
Understanding Paramotor Torque
On about Oct 27, 2010 a pilot took off with a Simonini based paramotor
that imparts significant torque. The brief flight unfolded through his
helmetcam footage which shows him twisting a bit immediately after
liftoff. He was climbing slowly and skewed leftward, twisting more to
the left as airspeed decreased until he finally swung all the
way around and plummeted hard into pavement from about 20 feet.
We can't tell from the helmet
cam footage exactly how the wing behaved, but it clearly wasn't
providing much support as evidenced from the nearly vertical hard fall.
He had several broken bones but, as the video shows, was in good spirits
and expects a full recovery with flight to follow.
Sadly, this is one of paramotoring's most common control-related crashes
although this is the worst outcome that I'm aware of. Thankfully this pilot gave consent to use
his helmet camera
footage so others could learn from it. If you have a mishap please share it on
USPPA.org's incident database for the benefit of all.
This is exactly the same type of accident seen in Risk and Reward
where the pilot twists on takeoff and flies into a tree.
That video admonishes pilots, who are experiencing unusual sensations, to
go hands up, power off but a better response is to "Reduce
power, reduce brakes, then steer." This applies if you
otherwise don't know what to do. And it should be automatic since, even
though it's not ideal for every situation, it's corrective for the
most likely causes of inflight motor flying maladies. It's NOT
advice for free flight pilots who come to grief for different reasons.
There are numerous other videos of this accident type.
http://www.youtube.com/watch?v=buKQReI0IFw
http://www.youtube.com/watch?v=DlPKt6woE4Q&feature=related
When is this likely?
A riser twist or stall/spin just after takeoff is most likely when:
1. You're on a high thrust, belt driven machine with lots of lean-back and
minimal torque countermeasure (usually offset risers).
While that tends
to be low hook-in machines, it's not about the hook-in point, it's about
the lean back and torque countermeasure. I've had it start to happen on several high
hook-in machines, including one with over-shoulder J-bars. Had I stayed
on the power, I would have spun all the way around. In fact, I've observed
more of these accidents in high hook-in machines, probably due to their much higher prevalence in the U.S.
2. Allowing the wing to go slightly right just before
liftoff.
This is subtle. When the wing pulls right and you're still on the ground, it imparts a slight left
twist. Plus, if the wing is to the right, you takeoff in a right bank,
possibly causing you to react with left brake. And left brake will also
be needed to counter the now-left-thrusting motor from causing MORE
right bank, getting that much closer to the excessive brake pull
necessary to spin the wing.
It's better if the wing is to your left slightly at liftoff.
3. A mis-adjusted harnesses can almost guarantee twisting after
launch.
As mentioned in #1, to counter torque's effect, you want the thrust line pushing on your
left shoulder (belt driven machines). But if the machine is
pushing on your right shoulder, it's adding to torque
twist—you're doomed. On one machine, whose owner had found it unflyable,
it turned out to be caused by a mis-adjusted harness.
4. You
don't let the machine turn right (twist left, bank right) as it naturally wants to, rather you
apply left brake to fly straight or, worse yet, try to turn left.
5. Something allows the risers' to move closer
together, making twisting easer. That was the case on one
machine with pivoting bars that could move inward.
Outward is OK, inward is very bad. That's the machine in the second
video above. I'd flown that unit and indeed had to throttle back in
order just to stay flying straight enough.
Any combination of these factors
makes the accident more likely and they might not come together for many
flights, lulling the pilot into thinking they're immune.
It's understandably surprising how it can happen after many many
uneventful flights. In the beach video above, that's a highly
experienced pilot on his regular paramotor. His wing had gone slightly
right, he was steering left to avoid the buildings, and stayed on full
power. Once the twist starts, it's easier to twist further—a cascade of
sorts. Plus, just as you lift off, going from being upright to leaned back
imparts a
gyroscopic precession twist to the left. It's a
momentary effect, but it gets the twist started, possibly beginning the
cascade that leads to spinning all the way around.
The only solution once a twist starts is "reduce power, reduce
brakes, then steer". Of course in this case its the power reduction that's
most critical. I've had to follow this advice on probably 5 different
machines to avoid spinning all the way around. In fact, for me at 145
pounds, its quite likely on big, powerful machines which is why, when
testing new gear, I'm rarely at more than half power on liftoff. You
have to use what's needed to get airborne but be ready to back off if
things start feeling fishy. It's particularly tough since the climb rate
suffers as you get sideways, making you reluctant to reduce power. You
just have to overcome that.
What about Protection
I get extremely annoyed by the seller of this machine, the Flattop,
when he berates other machines for their crashworthiness. The fact is that, in all the accidents
I've seen or investigated, if the pilot lands with the machine tilted
back, he gets significant protection--they all have "crush zones"
by virtue of their necessary construction. If the pilot lands
nearly vertical or tilted forward, the injuries are worse as they were in
this case. The surface has has a lot to do with it, too. I've seen (and
filmed) pilots walk away from serious crashes on Fly Products, Fresh
Breezes, Paratoys, SD and others because they landed on the machine
which gave way. This is from actual accidents. In fact, it's possible
the machine doesn't have ENOUGH give and transfers too much of the
energy to the pilot.
If you hear a seller crying with religious fervor about all the other
machines being "death traps" that says a LOT more about the seller's
trustworthiness than it does the other machines's crashworthiness. I'm a
big believer in an evidence-based assessment of reality and the evidence
suggests that most brands of paramotor, with a standard cage, have very
similar crashworthiness.
How to Prevent It
First of all, rehearse the response to unknown maladies. "Reduce
power, reduce brakes then steer." IF you're flying a high powered
machine, consider a less-than-full-power takeoff and make sure the wing
is overhead or slightly left before committing to flight. Be
ready to slightly reduce power after takeoff but don't be abrupt!
Adjust your harness so that the motor is as vertical as you can be
comfortable with and that the thrust line is as far left as possible.
Remember this can even happen to low power machines if the harness is
mounted wrong (gear drive units twist right).
Once you're familiar with the machine then doing an immediate full
power isn't as dangerous. Heres the news story, from
KXLY:
On Oct 27
BOUNDARY COUNTY, Idaho -- A North Idaho man who was paragliding was
saved by two bystanders who watched him crash in a remote area of
Boundary County last week.
Hoyt Patton has a passion for motorized paragliding, and that passion
grew deeper after last Tuesday, when he looked down at the pavement from
100 feet in the air and knew he was about to crash.
The motorized paraglider Patton used has a parachute with a motor
strapped to his back. Last Tuesday, Patton put on the paragliding device
and his helmet with an attached camera and began flying through the air
without trouble. After a few minutes a gust of wind knocked out his
motor and Patton crashed hard on the ground.
Two people witnessed Hoyt fall from the sky and called 911. Patton was
on the ground for several minutes, fighting to get up, but a broken
pelvis, disconnected femur, shattered arm and broken ribs kept him on
the ground.
The people eventually reached Patton and took him to get help.
Patton's body may be broken, held together with screws and pins much
like the flying contraption he loves so much, but his spirit isn't even
bruised.
"I am not broke. I have my family around me and I get to fly with a
smile on my heart," Patton said.
Hoyt was a competitive sky diver for decades, but six years ago he
discovered motorized paragliding and decided to take it up. This latest
accident is Patton's worst crash and it doesn't even phase him.
"When you think about hitting the ground when you're sky diving, you
think about finality, not if I am going to have a broken toe nail,"
Patton said.
He is comparing a broken toe nail to the damage he did to his arm.
Patton says his passion for life is why he lives so dangerously up in
the sky.
"I don't explain my life in any thing other miracles," Patton said.
Patton might need a few more miracles as he starts extensive rehab for
his injuries. He says its only a matter of time before he will be on his
paraglider skate boarding on air.
"Nothing is going to stop me now, " he said.
If you can't see the imbedded video below, click
here.
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At this point he has twisted 90 degrees to the wing,
looking towards his right hand, and still under power. This is the
natural torque twist direction. Once it starts, resistance to twisting
decreases because the lines move closer together.
Although we can't see what's happening with the wing,
it's likely that it was banked right since the motor is pushing him left
beneath it. We can also see that, since he is not in fact turning, there
is lots of left brake applied. Clearly forward motion stops and he
descends vertically, landing hard on pavement. One likely scenario is
that enough left brake was pulled for the wing to either spin or start
to spin.
My hat is off to Hoyt for sharing his video with the
news channel (KXLY) and thereby giving everybody a chance to learn.
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